The testing of blood or other body fluids for medical evaluation and diagnosis has traditionally been the exclusive domain of large, well-equipped central laboratories. While such laboratories can offer efficient, reliable, and accurate testing of a high volume of fluid samples, using a wide range of simple through complex procedures, they cannot offer immediate results. A physician typically must collect samples, transport them to a private laboratory, wait for the samples to be processed by the laboratory, and wait still longer for the results to be communicated, producing delays often reaching several days between collection of the sample and evaluation of the test results. Even in hospital settings, the handling of the sample from the patient's bedside to the hospital laboratory, the workload and throughput capacity of the laboratory, and the compiling and communicating of the results can produce significant delays. A need exists for testing apparatus which would permit a physician to obtain immediate results while examining a patient, whether in the physician's office, in the hospital emergency room, or at the patient's bedside during hospital daily rounds.
Traditional laboratory equipment is not readily adaptable to this end. The size, expense, and complexity of such equipment is prohibitive in itself, but a difficulty of equal magnitude is the skill level required to operate such equipment. Highly-trained laboratory technicians must perform the measurements in order to assure the accuracy and reliability, and hence the usefulness, of the results. To be effective, a real-time analysis device must overcome this limitation, by providing fool-proof operation for a wide variety of tests in relatively untrained hands. For optimum effectiveness, a real-time system would require minimum skill to operate, while offering maximum speed for testing, high accuracy and reliability, and cost effective operation, through maximum automation. Ideally, a successful device would eliminate operator technique as a source of error by eliminating the need for manual intervention.
Several prior art devices, while functional, have nonetheless failed to offer a complete solution. For example, the system disclosed in U.S. Pat. Nos. 4,301,412 and 4,301,414 to Hill, et al., employs a disposable sample card carrying a capillary tube and two electrodes. The sample card is inserted into an instrument to read the electrical potential generated at the electrodes. While simple conductivity measurements can be made with this system, there is no provision for the full range of tests which would be desired by a physician. Similarly, the device of U.S. Pat. No. 4,756,884 to Hillman, et al., provides limited testing with a transparent plastic capillary flow card which permits external optical detection of the presence of an analyte.
Some prior art devices of more general utility suffer the disadvantage that excessive manual intervention is necessary in the testing process. For example, U.S. Pat. No. 4,654,127 to Baker, et al., shows a single use sensing device having species-selective sensors in a test chamber. The operator must manually fill a sample chamber with the sample to be tested, manually input data to a reading instrument through a keyboard, and respond to a prompt from the instrument by closing the sample chamber, manually rotating a cylindrical reservoir to dispense calibrant onto the sensors, and then manually inserting the device into the reading instrument. When prompted by the instrument, a further manual rotation of the reservoir releases the sample to the sensors. Although equipment of this sort is capable of performing a useful range of tests, the high number of manual operations involved in interacting with the instrument produces a correspondingly high number of opportunities for operator error in timing or technique, which may have a detrimental impact on the trustworthiness of the measurements performed.